Method and apparatus for treating incontinence

ABSTRACT

An improved method, system and arrangement for treatment of urinary incontinence is disclosed, in which a portion of innervated smooth muscle ( 2 ) is transplanted and disposed around the urethra to provide a urethral sphincter ( 2 ). Electrical stimulation, by an implanted stimulator ( 1 ), maintains continuous tone in the sphincter. A remote controller ( 7 ) permits the sphincter ( 2 ) to be allowed to relax, and hence permit urine to flow out of the bladder.

FIELD OF THE INVENTION

This invention relates to prosthetic devices for the treatment ofurinary incontinence and, in particular, to prosthetic devices employingtransplanted tissue.

BACKGROUND OF THE INVENTION

The present invention is concerned with forms of incontinence causedwholly or partly by inadequate sphincter function. This may includeforms of stress incontinence, urge incontinence and total incontinence.The invention has been developed initially for use in treating maleincontinence and will be described principally with respect to thatapplication. However, it will be appreciated by those skilled in the artthat the invention is also applicable for use in treating femaleincontinence.

Incontinence is a major health problem, particularly with the ageingpopulation, for which there is no well-accepted medical treatment. Forfemales, surgically constructed slings are increasingly being used forstress incontinence and with increasing success. However, here is no lowrisk and reliably effective treatment for moderate to severe male stressincontinence particularly after treatment of prostate cancer. As theincidence of prostate cancer is increasing, this is a growing healthissue.

The internal sphincter of the urethra consists of smooth muscle cellsinterposed with elastic tissue and is located in the proximal urethra.Its constant tone is crucial to maintaining mechanical resistance in theproximal urethra sufficient to hold back the passive pressure exerted byurine in the bladder. Weakness in this area is a common cause of urinaryincontinence, for example after treatment for prostate cancer.

Prosthetic sphincter valves have been proposed in numerous forms,including mechanical, hydraulic and electrical devices which replace orsupplement the defective damaged internal sphincter of the urethra (e.g.PT 101841, SE 931516, GB 2265844, FR 2638964, WO97/01309 and U.S. Pat.No. 4,619,245). Electrical stimulation of the muscles of the sphincterhas also been proposed (DE 29614895). Other approaches have proposed theuse of external or implanted electrodes to stimulate existing sphincterfunction.

A variety of approaches have been proposed in relation to the electricalstimulation of the muscles of the sphincter, most of which are directedtowards stimulating an existing sphincter and/or muscles disposed about,for example, a bladder (DE 29614895).

Another group of prior art proposals for the treatment of incontinenceare directed towards the stimulation of sacral nerves and the like. Suchproposals again seek to use the existing muscle structures. (U.S. Pat.No. 4,771,779, U.S. Pat. No. 4,703,775, U.S. Pat. No. 4,607,639, U.S.Pat. No. 3,870,051, U.S. Pat. No. 4,688,575, U.S. Pat. No. 4,389,719 andU.S. Pat. No. 5,702,42).

Other stimulation means have been proposed, for example U.S. Pat. No.5,562,717, wherein stimulating electrodes are disposed on the skin of aperson to externally stimulate existing muscles to control incontinence.This method is disadvantageous in that it requires electrodes to bedisposed in a predetermined location of the person and be electricallyconnected to a power source therefore not allowing complete freedom.

It has also been proposed to implant part of a small skeletal musclefrom the thigh around the patient's urethra, and then to electricallystimulate the muscle to “retrain” it to function as a replacementsphincter (New Scientist, 29 Jun. 1996). However, this approach, even ifsuccessful, would require relatively high levels of electricalstimulation to allow sufficient contracture of the replacementsphincter.

It is an object of the present invention to provide an improvedprosthetic device for use in treating incontinence.

SUMMARY OF THE INVENTION

Broadly, the present invention utilises innervated smooth muscle toprovide an auxiliary sphincter. This is stimulated by a suitable devicein order to provide a functional sphincter in the patient. As aconsequence, the stimulator device can operate with lower powerconsumption, and produce a superior sphincter action.

According to a first aspect of the invention there is provided animplantable sphincter stimulator configured for operatively providingelectrical stimulation to a surgically implanted innervated smoothmuscle sphincter disposed about a urethra so as to control the flow ofurine therethrough, the stimulator including:

a stimulus generating unit in electrical communication with a receiver,the stimulus generating unit operatively configured to provide a firstpredetermined electrical stimulation signal adapted to contract saidsphincter, and a second predetermined signal adapted to allow saidsphincter to relax, one of said predetermined signals being selected inresponse to a signal received at the receiver from a remote controller.

In preferred embodiments, the stimulator applies the first stimulationsignal, unless a signal is received indicating that the patient wishesto empty the bladder. The second stimulation signal may be simply theabsence of a stimulation, a to lower level signal or an alternativesignal.

Preferably, the stimulation signal is one which will maintain acontinuous tone in the innervated sphincter. In other preferredembodiments of the invention the stimulation signal is pulsatile.Preferably, the stimulator provides multiple channel pulse generation.Preferably also, the stimulation pulse frequency is in the range of 0.25to 2.5 Hz and having a width in the range of 0.05 to 0.20 milliseconds.

Preferably the stimuli applied have a current less than or equal to 30mA. More preferably, the stimulation signal is generally rectangular andsymmetrical biphasic, although alternative biphasic pulses may be used.

Preferably, the sphincter stimulator includes a replaceable orrechargeable battery power source, preferably one which is in-siturechargeable, for example inductively.

Preferably, the signal to the receiver is communicated by microwave orradio means, optically or by magnetic energy and the receiverrespectively is a microwave, radio, photon or magnetic energy receiver.

Preferably, the stimulus generating unit includes a demodulatorresponsive to the received signal for providing a modulated signal to astimulus encoder which in turn provides a signal to a stimulus driver.The stimulator preferably includes two or more electrodes foroperatively delivering the stimuli to the sphincter. The stimuli maydiffer between electrodes, or may be the same at each.

Preferably, after the sphincter has been relaxed, the stimulator isadapted to supply the first stimulation signal to contract the sphincterwhen a predetermined signal to contract the sphincter is not received bythe receiver after a predetermined period.

Preferably, the sphincter stimulator includes a transmitter fortransmitting sphincter stimulator telemetry information indicative ofone or more parameters of the stimulator for detection remotely.Preferably, the information is transmitted by means of radio waves,microwaves, optically or by magnetic energy. More preferably, theparameters include one or more of the stimulation signal frequency,current, width and/or shape, and/or of the received signal strength andbattery status. Preferably, the stimulus generating unit includes aprocessing device with non-volatile memory.

Preferably, the receiver is configured to accept a remotely generatedsphincter stimulator calibration signal and in response, the stimulusgeneration unit selectively varies one or more of the stimulationsignals. More preferably, the calibration signal is transmitted inresponse to received sphincter stimulator telemetry information, forexample the telemetry signals from the stimulator.

Preferably, the stimulator is in electrical communication with thesphincter by at least one electrical lead having two or more electrodeswhich are operatively implanted into the sphincter at a predeterminedlocation. More preferably, the lead includes three electrodes disposedin an epimysal, cuff or tripolar configuration about the sphincter.

Preferably, the smooth muscle is taken from the smooth muscle of thebladder and transplanted about the urethra and having its circulationintact. Alternatively, the muscle is venous smooth, anococcygeus smoothmuscle, terminal ileum transplanted as a segment devoid of mucosa andhaving its circulation intact. A further alternative is the dartossmooth muscle from the scrotum or labia. In each case, the long axes ofthe muscle cells are disposed substantially circumferentially about thesphincter. Depending upon the muscle selected, the circulation may ormay not be transplanted intact. If the circulation is not transplantedintact, new vessels will need to be regrown, or otherwise provided.

According to a second aspect of the invention there is provided a systemfor use in treating bladder incontinence in a person, the systemincluding:

a portion of innervated smooth muscle tissue configured to define asphincter and implanted substantially circumferentially about theurethra of the person;

an implanted sphincter stimulator arranged so as to allow electricalstimuli to be applied to the sphincter; and

a non-implanted controller in communication with the sphincterstimulator for selectively triggering the generation of predeterminedelectrical stimulation signals to respectively contract the sphincter orallow the sphincter to relax.

Preferably, the smooth muscle is in the form of a strip and is generallyrectangular. More preferably, the strip has dimensions in the range from4.5 cm to 7.5 cm by 1.25 cm to 2.25 cm. Also preferable, the muscle isdisposed substantially fully around the urethra in a generallycylindrical arrangement such that the long axes of the muscle cells aresubstantially circumferentially aligned.

Preferably, the smooth muscle is selected from those described above.

Preferably, the system includes a sphincter as described above.

Preferably, the controller includes:

a transmitter;

means for generating a predetermined signal at the transmitter;

a power source; and

actuation means for selectively generating a signal such that on receiptof the signal, the sphincter stimulator provides the stimulation signalat its output for contracting the sphincter or allowing it to relax. Thesignals for selecting relaxation or contracture may be different, or thesame signal may trigger alternation of states.

One form of the controller, particularly for use by a physician, mayinclude a receiver for receiving the sphincter stimulator telemetryinformation signal from the sphincter stimulator. Preferably, the signalis transmitted by radio waves, microwaves, optically or by magneticenergy and receiver respectively is a radio, microwave, photon ormagnetic energy receiver.

Preferably, the system includes a remote sphincter stimulatorprogramming unit for selectively programming the sphincter stimulator toprovide a predetermined output. Preferably, one or more of thestimulation signal current, shape, frequency and width is variable inresponse to the calibration signal provided by the programming unit.More preferably, the programming unit includes a transceiver forproviding the programming signal to the stimulator. The programming unitmay conveniently be the physician controller.

According to a third aspect of the invention there is provided a methodof using an implantable sphincter stimulator for treating bladderincontinence, the method including the steps of disposing an innervatedsmooth muscle sphincter about a urethra, arranging one or moreelectrodes so as to allow stimulation of the neural structures of saidsphincter, said electrodes being connected to the sphincter stimulator,so that post implantation, a predetermined stimulation signal may beapplied by a stimulus generating unit to selectively contract thesphincter or allow it to relax.

Preferably, the method includes the step of transmitting the signal tothe sphincter stimulator by radio signals, microwaves, optically or bymagnetic energy.

Preferably, three electrodes are arranged in the sphincter in anepimysal, cuff or tripolar configuration.

Preferably, the sphincter is smooth muscle selected from thosepreviously described.

According to a fourth aspect of the invention there is provided a methodof treating incontinence including the steps of:

disposing an innervated smooth muscle sphincter around a urethra;

locating a plurality of electrodes in predetermined locations in thesphincter and electrically connecting the electrodes with an implantedsphincter stimulator; and

selectively actuating the sphincter stimulator to provide apredetermined stimulation signal to either contract the sphincter orallow it to relax in response to a remotely generated signal.

According to another aspect of the invention there is provided a methodof surgically implanting a sphincter stimulator in a system for treatingurinary incontinence, including the steps of:

implanting the innervated smooth muscle sphincter about the urethra in aperson;

implanting the electrodes into the sphincter at predetermined locations;and

implanting the sphincter stimulator, the arrangement being such that theelectrodes are electrically connected to the sphincter controller topermit stimulation signals from said sphincter stimulator to stimulatethe neural structures of said smooth muscle.

Implanting in this context includes transplanting from the same oranother person, or the use of externally prepared smooth muscle tissue.In each aspect, it is preferred that the implanted sphincter function soas to substantially prevent leakage of urine when contracted. Ingeneral, the main function of the innervated muscle prosthesis is toaugment function in the internal sphincter. It should not be used tooverride any natural sphincter function that may be preserved. Thesphincteric pressure exerted by the prosthesis should be sufficient torestore the net sphincteric resistance to its normal level of operation.Unnecessarily high pressure would not only be wasteful of internalstimulator energy but could also cause dangerous overfilling of thebladder. On the other hand, the pressure must be sufficiently high toprevent the leakage of urine.

The smooth muscle tissue may be selected from those described above, orany other suitable smooth muscle tissue. It will be appreciated by thoseskilled in the art that other types of smooth muscle may potentially beemployed as the implantable sphincter including alpha-adrenergicexcitatory innervation, cholinergenic excitatory or, inter alia,circular intestinal muscle.

One advantage of using smooth muscle tissue is that it physiologicallyperforms a sphincteric-like function and the muscle layer should be ableto be transplanted whilst maintaining its innervation, or allowing forits reinnervation, and blood supply. Moreover, smooth muscle of thetypes described is readily re-innervated by sympathetic nerves shouldthe existing innervation be damaged during surgery. Reinnervation maytake some time, for example, two to three weeks, after surgery.

Another advantages associated with the use of an innervated smoothmuscle sphincter in accordance with the present invention is that insmooth muscle, a long-lasting contracture (2-3 seconds) results from asingle neural stimulation. Accordingly, only a low frequency ofstimulation is required to produce a tetanic contraction especiallywhere it is moderated by neurotransmitter release.

The tension generated per unit cross-sectional area of smooth muscle isgreater than for skeletal muscle. Smooth muscle generates tension over awide length/tension relationship, that is, it continues to generatetension even when partially contracted. Smooth muscle is able tomaintain high tension with relatively low energy expenditure. Smoothmuscle tissue generally displays a persistent generation of tone duringlow frequency repetitive nerve stimulation.

A further advantage of the use of smooth muscle according to the presentinvention is that low frequency nerve stimulation causes the release ofa chemical transmitter. Stimulating the nerves within smooth muscleinvariably triggers a contraction because the neurotransmitter interactswith a receptor. The activated transmitter/receptor complex thenactivates a second messenger pathway and releases calcium ions frominternal stores. It is relevant that calcium is the final trigger in thecontraction of both skeletal, smooth or cardiac muscle. When storesrelease calcium they do so for extended periods of time, typically inthe order of several seconds. Therefore, if the exciting pathway istriggered repeatedly at low frequencies a sustained rise in calciumoccurs and the smooth muscle develops a contracture. That is, it doesnot relax between stimuli. In some smooth muscles, a few stimulidelivered every two seconds, for example, will lead to a sustainedcontraction.

An alternative way to excite smooth muscle is to stimulate it directlywhich produces quite long lasting contractions but only on applicationof very high stimulating voltages. Nerves have low thresholds foractivation, compared with muscles, and this, together with the lowfrequencies of activation required, means that stimulus spread will beavoided. Importantly, an electrical device can reasonably be expected tosurvive untouched for many years with such low usage demands.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by way ofexample only, with reference to the accompanying drawings in which:

FIG. 1 is a schematic illustration of a system for treating incontinenceaccording to the invention;

FIG. 2 schematically illustrates the implanted sphincter stimulator ofFIG. 1;

FIG. 3 schematically illustrates external and implanted parts of thesystem of FIG. 1;

FIG. 4 illustrates a sphincter stimulator programming unit and sphincterstimulator of the system of FIG. 1;

FIG. 5 is an alternative schematic illustration of the system of FIG. 1showing a preferred configuration of electrodes; and

FIG. 6 is an enlarged view of the electrode configuration of FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring in general to FIGS. 1 to 6, there is illustrated animplantable sphincter stimulator 1 for selectively providing electricalstimulation to an innervated smooth muscle sphincter 2 disposed about aurethra 3 for controlling the flow of urine.

Stimulator 1 includes a signal processing unit 4 in electricalcommunication with a receiver 5. Signal processing unit 4 is configuredto provide a predetermined electrical stimulation signal at a firstoutput 6 of stimulator 1 in response to a signal generated remotely bycontroller 7 and applied at receiver 5 such that processing unit 4selectively provides the stimulation signal to either contract sphincter2 to substantially block the flow of urine along the urethra 3 or toallow sphincter 2 to relax and allow urine to flow.

Referring to FIG. 2 particularly, signal processing unit 4 includes ademodulator 8 responsive to the signal received at receiver 5 forproviding a modulated signal to a stimulus encoder 9 which in turnprovides a signal to a stimulus driver 10 which provides the stimulatedsignal at sphincter stimulator output 6.

Once sphincter 2 is allowed to relax, processing unit 4 includes meansto supply a stimulation signal at output 6 to contract sphincter 2 whena predetermined signal to contract the sphincter is not received bysignal processing unit 4 via receiver 5 for a predetermined time period.In the preferred implementation, the processing unit 4 provides stimuliadapted to contract the sphincter unless a signal is received, inresponse to which the stimuli is turned off, and the sphincter relaxes.

The signal is communicated to sphincter stimulator 1 by means of radiofrequency waves and receiver 5 is an RF receiver. If the casing of thestimulator is made of titanium, and the receiver is inside, then afrequency of 8-10 kHz is preferred. If the casing is made of siliconerubber or the like, then 8-10 MHz is preferred.

In other embodiments of the invention, the signal may be communicatedoptically in the range 630 nm to 1400 nm to sphincter stimulator 1 andreceiver 5 is a photon detector in the form of a PMT, photo-diode orother suitable detector.

In yet other embodiments of the invention, the signal is communicated tosphincter stimulator 1 by microwave means and receiver 5 is a microwavereceiver. In such embodiments, the microwave signal has a frequency inthe range of 0.9 to 2.5 GHz. Alternatively, the signal is communicatedto sphincter stimulator 1 by magnetic means and receiver 5 is a magneticenergy receiver. Any other suitable communication arrangement may beused.

As is best illustrated in FIG. 3, controller 7 includes the RFtransmitter which is driven by a means for generating the controlsignal. Controller 7 further includes actuation means for selectivelygenerating the control signal at transmitter 11.

Part of transmitter 11 is also a receiver for receiving an informationsignal indicative of at least one parameter of the sphincter stimulatorand provided by the sphincter stimulator. The telemetry informationsignal is transmitted to the controller by means of a transmitterdisposed within receiver 5. In embodiments of the invention wheremicrowaves are employed to communicate either the control signal ortelemetry information signal, transceiver 11 of controller 7 isconfigured to transmit and receive microwave radiation. In embodimentswhere the control signal is transmitted optically, transceiver 11includes a photon detector in the form of a PMT or solid state deviceand a light source having a predetermined output. In embodiments of theinvention where the control signal and the sphincter stimulatorinformation signal are transmitted by magnetic energy, the transmitterreceiver 5 functions as a passive proximity card and controller 7functions as the active proximity card reader.

FIG. 2 illustrates a stimulation signal in the form of a pulse. Thepulse is generally rectangular and symmetrically biphasic. In otherembodiments of the invention, not illustrated, sphincter stimulator 1provides multiple channel pulse generation at output 6. The stimulationsignal is selected so as to provide a substantially continuous tone inthe sphincter.

The stimulation signal provided at output 6 has a substantially constantcurrent less that or equal to 30 mA, and preferably of the order of 15mA.

The stimulation pulse frequency provided to sphincter 1 by output 6 isin the range of 0.25 Hz to 2.5 Hz and is preferably 2 Hz. Thestimulation pulse width is in the range of 0.05 ms to 0.2 ms and ispreferably 0.15 ms. It should be noted that the device is currentregulated, and accordingly the stimulation voltage will vary with theresistance of the muscle tissue between the electrodes. Typical valuesfor the voltage are between 0.2 and 7 volts.

It should be noted, however, that these parameters are variable and areconfigured for each person.

Preferably, the smooth muscle is taken from the smooth muscle of thebladder and transplanted about the urethra and having its circulationintact. Alternatively, the muscle may be venous smooth, anococcygeussmooth muscle, terminal ileum transplanted as a segment devoid of mucosaand having its circulation intact. A further alternative is the dartossmooth muscle from the scrotum or labia. Any other suitable muscle maybe employed. In each case, the long axes of the muscle cells aredisposed substantially circumferentially about the sphincter.

The muscle is generally in the form of a rectangular strip such that thelong axes of the muscle cells are disposed substantially lengthwisealong the strip. The muscle is then disposed substantially fully aroundthe urethra in a generally cylindrical arrangement such that the longaxes of the muscle cells are substantially circumferentially disposedabout the urethra. Preferably, the strip is completely disposed aroundthe urethra.

The muscle strip has dimensions 6 cm by 2 cm and is preferably providedin the range from 4.5 cm to 7.5 cm by 1.25 cm to 2.25 cm.

The stimulation signal is provided at output 6 of sphincter stimulator 1is supplied to sphincter 2 by an electrode implanted into the sphincterat a predetermined location and an electrical lead 16 being disposedintermediate. As is best illustrated in FIG. 6, lead 16 includes threeelectrodes disposed in a tripolar configuration about sphincter 2 andhaving means to electrically connect to lead 16. In other embodiments ofthe invention, the three electrodes are disposed in a cuff or epimysalconfiguration about the sphincter.

Electrode leads may extend between the pulse generator and theelectrodes, allowing some “slackness” in their length to account fornormal body movements.

As is best illustrated in FIGS. 5 and 6, the configuration of theelectrodes are disposed in a tripolar configuration. Simple tripolarelectrodes are the least expensive alternative, are relatively easy toimplant and can be used to stimulate the transplanted smooth muscle.Their exposed metallic surfaces usually consist of a cathode alignedbetween two anodes.

In the epimysial configuration, the electrodes are sutured directly ontothe surface of a muscle. These electrodes are implemented whenstimulation of a motor nerve trunk is impractical, however, this is notnecessarily always the case.

In the cuff electrode configurations are employed in alternativeembodiments and are contained within an insulating sheath substantiallycircumferentially around the circumference of the transplantedsphincter. They are capable of stimulating the embedded nerve fibresmaximally while keeping the stimulus field local to the transplant.

In other embodiments of the invention, not illustrated, the sphincterstimulator includes a second output such that one of the sphincterstimulator outputs provides a signal to contract the sphincter and theother output provides a stimulation signal to allow the sphincter torelax or contract to a lesser extent. In this embodiment, each of thefirst and second outputs of the sphincter stimulator each include a leadhaving three outputs in a tripolar configuration about the sphincter. Inyet other embodiments, the first and second outputs each include a leadhaving three electrodes disposed in a cuff or epimysal configurationabout the sphincter.

It will be appreciated that in normal use, only two of the threeelectrodes will be used to deliver stimuli. The third electrode isprovided as a spare, in the event that one of the electrodes ceases tofunction However, it is contemplated that the present invention coulduse a more complicated set of stimuli, or more electrodes.

Sphincter stimulator 1 includes a replaceable battery power source 17,not illustrated in FIG. 2. In one implementation, battery 17 is inelectrical communication with signal processing unit 4 such that thecontrol signal provided by controller 7 to sphincter stimulator 1inductively provides energy to recharge the battery. In anotherimplementation, in the case of radio frequency transceiving between theand sphincter stimulators, the signal is provided by modulating the RFsignal such that the signal processing unit extracts the control signaland provides the battery with remaining power from the RF signal.

As is best illustrated in FIG. 4, RF transceiver 5 of stimulator 1 iscommunicable with a third output of processing unit 4 for transmittingsphincter stimulator telemetry information indicative of one or more theparameters of the sphincter stimulator for remote detection. Theinformation is transmitted by radio frequency signals, however, in otherembodiments of the invention the sphincter stimulator information istransmitted by microwave means, optical means or by magnetic energy. Thesphincter stimulator information signal includes information regardingparameters such as stimulation signal-frequency, current, width and/orshape, and received signal strength and battery status. This is usefulfor use in a controller intended for use by physicians.

A remote sphincter stimulator programming unit 13 is adapted to receivethe sphincter stimulator information provided by receiver 5. Thesphincter stimulator programming unit includes a transceiver 14 forproviding a calibration signal to stimulator 1 which, in response,selectively varies one or more of the output properties of stimulator 1.The calibration signal is preferably transmitted in response toreceiving the sphincter stimulator telemetry information. Thecalibration signal includes coding to selectively vary the outputcurrent, shape, frequency and/or width. Conveniently, the remotesphincter stimulator programming unit is integrated into the physiciancontroller.

The preferred embodiments of the invention also provide a method oftreating urinary incontinence in a person including the steps ofdisposing the implanted smooth muscle sphincter substantially around aurethra, locating a plurality of electrodes in predetermined locationsin the sphincter and electrically connecting them with an implantedsphincter stimulator as hereinbefore described.

The sphincter stimulator is then selectively actuated on receipt of thecontrol signal to provide the predetermined stimulation signal to eithercontract the sphincter or allow it to relax. The method includesproviding the stimulation signal to contract the urethra or allow it torelax from output 6 of sphincter stimulator 1. In other embodiments ofthe invention, however, the stimulation signal to contract the sphincterabout the urethra is provided by a separate output of sphincterstimulator 1 to that which provides a stimulation signal to allow theurethra to relax.

There is also provided a method of surgically implanting a sphincterstimulator system as hereinbefore described in a person for treatingincontinence, the method including the steps of implanting the smoothmuscle sphincter substantially about the urethra in a person, implantingthe sphincter stimulator in the person proximal to the implantedsphincter and implanting electrodes into the sphincter at predeterminedlocations and electrically connecting the sphincter stimulator with thesmooth muscle sphincter.

Other preferred embodiments provide a stimulus system including circuitmeans defining a single channel electrical pulse generator, power supplymeans, a control circuit to allow a transplanted sphincter to relax, aseparate control circuit to adjust pulse parameters, two or morestimulus electrodes, and leads connecting the stimulator to theelectrodes.

The prosthetic sphincter includes a sheath of innervated orreinnervatable muscle tissue taken from the selected muscle andtransplanted around the urethra. In one embodiment, a segment of distalsmall intestine, 2-3 cm long, on a vascular pedicle is isolated and theremaining intestine is rejoined by end to end anastomosis. The isolatedsegment is opened along its antimesenteric border and the mucosa isdissected away.

The isolated segment is drawn down to the neck of the bladder. It isthen taken around the bladder neck, so that the circular muscle isdisposed substantially circumferentially with respect to the neck, andthe cut antimesenteric borders are sewn together to create a close fitaround the neck of the bladder. If necessary, the circumferential lengthis reduced to create a close fit. The newly created and vascularisedsphincter is secured in place by sewing it to the superficial connectivetissue of the bladder neck. A stimulating electrode assembly is sewn tothe transplanted intestine, with the axis of the electrode assembly atright angles to the circular muscle, adjacent to the entry of thevessels from the vascular pedicle. The anchoring ligatures penetrate thesphincter and are secured to the underlying bladder neck.

In an alternative embodiment, the sphincter augmentation is made bydissecting the anococcygeus muscles from their spinal insertions, anddrawing the freed muscle around the bladder neck. The sphincter may alsobe created from a section of muscular vein, venous smooth muscle, theterminal ilium and transplanted as a segment devoid of mucosa and havingits circulation intact, or the dartos smooth muscle from the scrotum orlabia.

The stimulus pulse generator transfers electrical pulses to theelectrodes and these pulses are converted into action potentials in thenerves transplanted with the muscle sphincter or in the nerves whichre-innervate the sphincter after surgery.

All implanted circuitry is preferably sealed and encased in abiologically inert material such as a biocompatible silicone material.The metallic electrodes and leads are preferably of Platinum-Iridiumalloy. The connecting wires are preferably insulated with a siliconecoating and lead to an implanted control unit placed between theabdominal muscle and skin.

The stimulator is required to maintain continuous tone in thetransplanted sphincter sufficient to hold urine in the bladder withoutleakage by continuous stimulation. To release urine, an external controlunit using, for example, a radio frequency signal will turn off theinternal unit to halt the stimulation of the sphincter, and is shownschematically in FIG. 3.

Alternative embodiments of the invention employ microwave or opticalmeans, for example, in the form of infra-red radiation, to communicatethe control signal to the sphincter stimulator, and the sphincterstimulator includes a corresponding receiver at or near the skin of theperson.

The person would hold the external device adjacent the skin over theimplant (and push an actuation button) to allow the transplantedsphincter to relax and urine to flow. After bladder emptying, thepatient would then push the button again to resume sphincteric pressure.As described, if the user forgets to push the button to close thesphincter, the stimulator could be programmed to resume operationautomatically after a given time.

The advantages of this system are twofold. Firstly, the patient does notneed to hold the external control unit against their skin for the wholeperiod of bladder emptying. They simply initiate the process and canthen put the unit aside if desired. The second advantage is that such asystem allows the stimulator circuitry to be adjusted externally.

In embodiments where the signal is communicated magnetically, apermanent magnet is placed on the surface of the skin directly over thelocation of the implanted control circuit. The circuit is designed todetect the presence of the magnetic field and shut off the stimulationaccordingly. To empty the bladder, therefore, the person simply places amagnet over the implant for the time period required to empty thebladder. A small permanent magnet is a convenient item to carry aroundand requires no batteries. One disadvantage of such a system is that amagnetic detector needs to be added to the implanted device and this, inturn, requires more power from the internal batteries.

It is envisaged that the requirements of the stimulator may change, bothpost-operatively and with alteration of the preserved sphinctericresistance as the person ages. Access to the implanted device viasurgery for the purpose of hardware adjustment is, of course,undesirable. Therefore, adjustment of the stimulus parameters via anexternal radio link to the sphincter stimulator programming unit 13 is apreferred feature of the system.

It will be appreciated that various modifications and alterations may bemade to the system described above without departing from the scope andspirit of the invention.

1. An implantable sphincter stimulator configured for operativelyproviding electrical stimulation to a surgically implanted innervatedsmooth muscle sphincter so as to control the flow of a bodily substancetherethrough, the stimulator including: a stimulus generating unit inelectrical communication with a receiver, the stimulus generating unitoperatively configured to provide a first predetermined electricalstimulation signal adapted to contract said sphincter, and a secondpredetermined signal adapted to allow said sphincter to relax, one ofsaid predetermined signals being selected in response to a controlsignal received at the receiver from a remote controller.
 2. A sphincterstimulator according to claim 1 wherein the stimulation signal is suchas to provide a continuous tone in said sphincter.
 3. A sphincterstimulator according to claim 2 wherein the stimulation is pulsatile. 4.A sphincter stimulator according to claim 3 wherein the stimulationsignal is generally rectangular and symmetrical biphasic.
 5. A sphincterstimulator according to claim 4 wherein the stimulation signal currentis less than or equal to 30 mA.
 6. A sphincter stimulator according toclaim 3 wherein the stimulation pulse frequency is in the range of 0.025to 2.5 Hz.
 7. A sphincter stimulator according to claim 3 wherein thestimulation pulse has a width in the range of 0.05 to 0.20 milliseconds.8. A sphincter stimulator according to claim 1 wherein the controlsignal is communicated by RF, microwave, optically or magnetically.
 9. Asphincter stimulator according to claim 1 wherein the stimulusgenerating unit includes a demodulator responsive to the received signalfor providing a modulated signal to a stimulus encoder which in turnprovides a signal to a stimulus driver which provides the stimulationsignal at selected ones of the stimulator outputs.
 10. A sphincterstimulator according to claim 1 wherein after the sphincter has relaxed,the stimulator includes means to supply the first stimulation signal ata selected one of its outputs to contract the sphincter when apredetermined signal to contract the sphincter is not received by thereceiver for a predetermined period.
 11. A sphincter stimulatoraccording to claim 1 including a transmitter for transmitting sphincterstimulator telemetry information indicative of one or more parameters ofthe stimulator for detection remotely.
 12. A sphincter stimulatoraccording to claim 11 wherein the information is transmitted by the samecommunications means as the control signal.
 13. A sphincter stimulatoraccording to claim 11 wherein the parameters include one or more of thestimulation signal frequency, current, width and/or shape, or receivedsignal strength or battery status.
 14. A sphincter stimulator accordingto claim 11 wherein the receiver is configured to accept a remotelygenerated sphincter stimulator calibration signal and in response, thesignal processing unit selectively varies one or more of the outputproperties of the sphincter stimulator.
 15. A sphincter stimulatoraccording to claim 14 wherein the calibration signal is transmitted inresponse to received sphincter stimulator telemetry information.
 16. Asphincter stimulator according to claim 1 wherein the stimulationgenerating unit is operatively connected to the sphincter by one or moreelectrical leads, each having one or more electrodes.
 17. A sphincterstimulator according to claim 16 wherein the lead includes threeelectrodes disposed in an epimysal configuration about the sphincter.18. A sphincter stimulator according to claim 16 wherein the leadincludes three electrodes disposed in a cuff configuration about thesphincter.
 19. A sphincter stimulator according to claim 16 wherein thelead includes three electrodes disposed in a tripolar configurationabout the sphincter.